C++/Class/Class Basics

Address class: class definition and implementation

<source lang="cpp">

1. include <iostream>
2. include <cstring>

using namespace std; class Address {

 char name[40];
 char street[40];
 char city[30];
 char state[3];
 char zip[10];

public:

 void store(char *n, char *s, char *c, char *t, char *z);
 void display();

}; void Address::store(char *n, char *s, char *c, char *t, char *z) {

 strcpy(name, n);
 strcpy(street, s);
 strcpy(city, c);
 strcpy(state, t);
 strcpy(zip, z);

} void Address::display() {

 cout << name << endl;
 cout << street << endl;
 cout << city << endl;
 cout << state << endl;
 cout << zip << endl;

} int main() {

 Address a;
 a.store("C", "11 Lane", "W", "In", "4");
 a.display();
 return 0;

}

      </source>

A simple class with member variable, constructor, destructor

<source lang="cpp">

1. include <iostream>

using namespace std; class who {

 char name;

public:

 who(char c) { 
    name = c;
    cout << "Constructing who";
    cout << name << endl;
 }
 ~who() { 
    cout << "Destructing who: " << name << endl; 
 }

}; who makewho() {

 who temp("B");
 return temp;

} int main() {

 who ob("A");
 makewho();
 return 0;

}

      </source>

Assign object1 to object2

<source lang="cpp">

1. include <iostream>

using namespace std; class BaseClass {

 int a;

public:

 void load_a(int n) { 
   a = n; 
 }
 int get_a() { 
   return a; 
 }

}; class DerivedClass : public BaseClass {

 int b;

public:

 void load_b(int n) { 
    b = n; 
 }
 int get_b() { 
    return b; 
 }

}; int main() {

 DerivedClass object1, object2;
 object1.load_a(5);
 object1.load_b(10);
 
 object2 = object1;
 cout << "Here is object1"s a and b: ";
 cout << object1.get_a() << " " << object1.get_b() << endl;
 cout << "Here is object2"s a and b: ";
 cout << object2.get_a() << " " << object2.get_b() << endl;
 return 0;

}

      </source>

Class forward declaration

<source lang="cpp">

1. include <iostream>

using namespace std; class pr2; // class pr1 {

 int printing;
 

public:

 pr1() { 
    printing = 0; 
 }
 void set_print(int status) { 
    printing = status; 
 }
 
 friend int inuse(pr1 object1, pr2 object2);

}; class pr2 {

 int printing;
 

public:

 pr2() { 
    printing = 0; 
 }
 void set_print(int status) { 
    printing = status; 
 }
 
 friend int inuse(pr1 object1, pr2 object2);

}; int inuse(pr1 object1, pr2 object2) {

 if(object1.printing || object2.printing) return 1;
 else return 0;

} int main() {

 pr1 p1;
 pr2 p2;
 if(!inuse(p1, p2)) 
    cout << "Printer idle\n";
 cout << "Setting p1 to printing...\n";
 p1.set_print(1);
 if(inuse(p1, p2)) 
    cout << "Now, printer in use.\n";
 cout << "Turn off p1...\n";
 p1.set_print(0);
 if(!inuse(p1, p2)) 
    cout << "Printer idle\n";
 cout << "Turn on p2...\n";
 p2.set_print(1);
 if(inuse(p1, p2)) 
    cout << "Now, printer in use.\n";
 return 0;

}

      </source>

Declare class instance

<source lang="cpp">

1. include <iostream>

using namespace std; class myclass {

 int a;

public:

 myclass(int x) { 
    a = x; 
 } 
 int geta() { 
    return a; 
 }

};

int main() {

 myclass ob(4);
 cout << ob.geta();
 return 0;

}

      </source>

Declare Class instance and use them

<source lang="cpp">

1. include <iostream>
2. include <cstring>

using namespace std; class Book {

 char title[80];             // book title
 char author[40];            // author
 int number;                 // number in library

public:

 void store(char *t, char *name, int num);
 void show();

}; void Book::store(char *t, char *name, int num) {

 strcpy(title, t);
 strcpy(author, name);
 number = num;

} void Book::show() {

 cout << "Title: " << title << endl;
 cout << "Author: " << author << endl;
 cout << "Number on hand: " << number << endl;

} int main() {

 Book book1, book2, book3;
 book1.store("D", "t", 2);
 book2.store("T", "v", 2);
 book3.store("T", "e", 1);
 book1.show();
 book2.show();
 book3.show();
 return 0;

}

      </source>

Init Object array

<source lang="cpp">

1. include <iostream>

using namespace std; class CharClass {

 char ch;

public:

 CharClass(char c) { 
    ch = c; 
 }
 char get_ch() { 
    return ch; 
 }

}; int main() {

 CharClass ob[10] = { 
   CharClass("a"), 
   CharClass("b"), 
   CharClass("c"), 
   CharClass("d"), 
   CharClass("e"), 
   CharClass("f"), 
   CharClass("g"), 
   CharClass("h"), 
   CharClass("i"), 
   CharClass("j")
 };
 int i;
 for(i = 0; i <10; i++) 
   cout << ob[ i ].get_ch() << " ";
 cout << endl;
 return 0;

}

      </source>

Simplest class definition

<source lang="cpp">

1. include <iostream>

using namespace std; class SimpleClass {

 int len;

public:

 SimpleClass(int l);

}; SimpleClass::SimpleClass(int l) {

 len = l;
 int i;
 for(i = 0; i <len; i++) 
    cout  << "*";

} int main() {

 SimpleClass l(10);
 return 0;

}

      </source>